Cascaded routers: no internet access when second router not use NAT
Here is my setup:
[pre]
WAN
|
-------------------------------
| 74.96.170.x (WAN IP) |
| Router1(Verizon FiOS Router) |
| Model: MI424WR-GEN2 (Rev F) |
| Firmware: 20.21.0.2 |
| Def router: 74.96.170.1 |
| 192.168.1.1 (Local IP) |
-------------------------------
|
---------------------------
| 192.168.1.22 (WAN IP) |
| Router2(Linksys) |
| Model: WRT54GL v1.1 |
| Firmware: v4.30.16 |
| Def Router: 192.168.1.1 |
| 192.168.2.1 (Local IP) |
---------------------------
|
----------------------------
| Computer 192.168.2.160 |
| Def Router: 192.168.2.1 |
"q.route" 120L, 4441C written
[m.wang@m-wang-ltm2:/Users/m.wang/m/Network]
$ more q.route
Cascaded routers: no internet access when second router not use NAT
Here is my setup:
[pre]
WAN
|
-------------------------------
| 74.96.170.x (WAN IP) |
| Router1(Verizon FiOS Router) |
| Model: MI424WR-GEN2 (Rev F) |
| Firmware: 20.21.0.2 |
| Def router: 74.96.170.1 |
| 192.168.1.1 (Local IP) |
-------------------------------
|
---------------------------
| 192.168.1.22 (WAN IP) |
| Router2(Linksys) |
| Model: WRT54GL v1.1 |
| Firmware: v4.30.16 |
| Def Router: 192.168.1.1 |
| 192.168.2.1 (Local IP) |
---------------------------
|
----------------------------
| Computer 192.168.2.160 |
| Def Router: 192.168.2.1 |
| NO iptables, basic setup |
----------------------------
[/pre]
On computer, I have:
[pre]
# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default 192.168.2.1 0.0.0.0 UG 2 0 0 enp2s0
loopback localhost 255.0.0.0 UG 0 0 0 lo
192.168.2.0 * 255.255.255.0 U 0 0 0 enp2s0
[/pre]
On Router2, I have:
[pre]
Routing Table Entry List
Destination LAN IP | Subnet Mask | Gateway | Hop Count | Interface
192.168.2.0 255.255.255.0 0.0.0.0 1 LAN & Wireless
192.168.1.0 255.255.255.0 0.0.0.0 1 WAN (Internet)
0.0.0.0 0.0.0.0 192.168.1.1 1 WAN (Internet)
[/pre]
Router2's Operating Mode is Gateway. On Router1, I have:
[pre]
[Router1] Routing Table
Name Destination Gateway Netmask Metric Status
Network (Home/Office) 192.168.2.0 192.168.1.22 255.255.255.0 0 Applied
Network (Home/Office) 192.168.1.0 192.168.1.1 255.255.255.0 0 Applied
Routing Protocol: Internet Group Management Protocol (IGMP)
Default Gateway: 74.96.170.1
[/pre]
On computer, I can run tcptraceroute to yahoo.com OK:
[pre]
# tcptraceroute yahoo.com
Selected device enp2s0, address 192.168.2.160, port 46596 for outgoing packets
Tracing the path to yahoo.com (206.190.36.45) on TCP port 80 (http), 30 hops max
1 192.168.2.1 0.610 ms 0.729 ms 0.735 ms
2 192.168.1.1 1.843 ms 1.378 ms 1.363 ms
3 l100.washdc-vfttp-107.verizon-gni.net (96.241.146.1) 13.620 ms * *
... /* It reached the destination. */
[/pre]
I want to change Router2's Operating Mode from "Gateway" to "Router" because I
want to turn off NAT on Router2 so that I can access all computers attached to
Router2 by their individual IP instead of using port forwarding at Router2.
The problem is after the mode change from "Gateway" to "Router", and regardless
whether I disable RIP or enable RIP, and on what interfaces it is enabled, computer
192.168.2.160 does not have internet connection.
Observations:
[0] INTRAnet works as I can reach computer 192.168.2.160 from computer behind Router1
192.168.1.x and vice versa.
[1] ping and traceroute *work* on Router2 itself using the built-in dianostic tool.
[2] nslookup on computer 192.168.2.160 always works on new lookup. It uses
192.168.2.1 as the resolver.
[3] tcptraceroute stops after step 2:
[pre]
# tcptraceroute yahoo.com
Selected device enp2s0, address 192.168.2.160, port 45999 for outgoing packets
Tracing the path to yahoo.com (98.139.183.24) on TCP port 80 (http), 30 hops max
1 192.168.2.1 2.553 ms 0.534 ms 0.638 ms
2 192.168.1.1 1.342 ms 0.964 ms 0.867 ms
3 * * *
[/pre]
[4] tcpdump shows that computer 192.168.2.160 tries to reach out and nothing is returned:
[pre]
13:34:03.172828 IP 192.168.2.160.45999 > 98.139.183.24.http: Flags [S], seq 1122548929, win 0, length 0
13:34:06.175786 IP 192.168.2.160.45999 > 98.139.183.24.http: Flags [S], seq 1122548929, win 0, length 0
13:34:09.178804 IP 192.168.2.160.45999 > 98.139.183.24.http: Flags [S], seq 1122548929, win 0, length 0
[/pre]
This is not expected because NAT to internet should still be done by Router1, no? Computer
behind Router1 with IP 192.168.1.x has internet connection.
[5] It looks like I cannot change the Routing Table Entry on Router2. I do not think I need to change anything,
just an observation.
[6] If I use LAN to LAN connection, then both intranet and internet works. [The internet IP of Router2 can be
anything not in the same subnet of the Router1, and DHCP on the local side should be disabled to avoid conflict
with the the DHCP on Router1].